Since the late 1980s, there has been a growing interest in biologically-active components in plants and animals, and in the effect that these compounds may have in preventing and alleviating human disease and promoting optimal health. The laxative properties of dietary fibre-rich wheat bran are well known. Specifically engineered food products rich in biologically-active phytochemicals may also have an important role to play in areas of protection against the so-called "chronic diseases": cardiovascular disease, diabetes, renal disease and the major cancers. Furthermore, the number of health-conscious consumers is at an all time high. Individuals are taking control of their own health, of which diet plays an important part. Functional foods, nutraceuticals and medical foods represent an exciting and rapidly growing area of Food Science and Technology (ref. 1 --a list of references appears immediately preceding the claims).
Wheat-based products manufactured by a combination of traditional and new technologies have the potential to capture a considerable share of the expanding functional foods market. Currently, foods made from wheat constitute the major source of dietary fibre in the diet of US and Canadian consumers. The accumulated science supports the association between intake of dietary fibre and bowel regularity. In addition, dietary fibre is suggested as having protective effect against colon and breast cancers.
Commercial milling of wheat into flour aims at the maximum extraction of the starch-rich endosperm with the minimum possible contamination by bran and germ, which form the by-products of the flour milling industry. Wheat germ is a unique source of highly concentrated biologically-active components. Wheat germ offers three times as much protein of high biological value and is the richest known source of tocoperhols (vitamin E) of plant origin and a rich source of agglutinin and several B-group vitamins, especially thiamin, riboflavin, niacin, pyridoxine and pantothenic acid (ref. 2). Similarly, wheat bran is a rich source of dietary fibre and phytochemicals, especially phytic acid, which is considered to be a natural antioxidant and is believed to play a role in health promotion (ref. 3). Phytic acid is also used as a complexing agent for the removal of traces of heavy metal ions and as a starting material in manufacture of inositol. Phytic acid content of cereals varies from about 0.7 to 1% and most of it is located in the bran component of wheat.
In ethanol production, starch is transformed into ethanol and carbon dioxide and other wheat constituents, such as proteins, are not utilized by fermenting yeasts and accumulate in the beerstillage. However, the proteins are denatured as a result of the heat treatment required for starch gelatinization and ethanol distillation in the process, and are used as animal feed in such forms as dried distiller's grain and solubles (DDGS), which contains about 20 to 40% protein on dry weight basis. A dry milling process may be used to facilitate the conversion of starch to dextrins and alcohol by yeast and/or enzyme.
Accordingly, phytochemicals-rich wheat germ and bran can be physically separated from each other and from the starch-rich endosperm and used as source(s) of wheat germ tocopherols, agglutinin, B vitamins, phytic acid and saponins. The endosperm fraction or flour can be used as a source of the water-soluble fibre and protein fractions. In addition, distillers dried grains and solubles (DDGS) can serve as source of valuable carbohydrate and protein fractions and biologically active secondary plant metabolites.
Proteins represent about 8 to 15% of whole wheat kernel weight and is the second most abundant group of molecules in wheat, next only to starch which accounts for up to about 80% of the kernel weight. Wheat proteins in normal wheat flour form gluten upon mixing with water and result in a dough with a unique viscoelasticity. This property has been exploited in the gluten industry where dough is washed with water and separated into starch and gluten. The starch and gluten are used in many food and non-food applications. Despite the many applications, the market value for vital wheat gluten is low and is much affected by the market demand for starch.
Wheat or its flour treated with heat loses its ability to form gluten as a result of denaturation of wheat gluten forming proteins. In traditional applications where this property is required, the lack of viscoelasticity of denatured gluten renders the proteins useless. Consequently, proteins in the downstream of wheat processing, such as ethanol production, are grossly underutilized.
Although there is an abundance of research (ref. 4) in breadmaking and other utilizations of wheat proteins where the viscoelastic properties of gluten is essential, little information is available on the production and application of soluble wheat proteins and wheat protein-fibre products.
U.S. Pat. No. 5,061,497 (Kovach) discloses a process for the production of a high-protein and high fibre bakery ingredient from cereal grains treated with alpha-amylase, followed by centrifugation and drying of the insoluble product. The objective in the Kovach disclosure is the production of a product which is not soluble in water and can be used only as a bakery ingredient.
Soluble products have been produced from the water extract of grains (refs. 5, 6). However, none of the products obtained previously were produced using a combination of enzyme treatment and ultrafiltration, purification, and concentration. As a result, these products are low in protein content, and have marginal functional properties.